Process for preparing 3-substituted-methyl-3-cephem derivatives

ABSTRACT

Various 7-amino-3-substituted-methyl-3-cephem-4-carboxylic acids and lower alkylsilyl derivatives such as 7-amino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylic acid iodide and trimethylsilyl 7-trimethyl-silylamino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylate iodide are valuable intermediates in the preparation of new and novel antibacterial agents. A new process for the preparation of these acids and the derivatives has been devised.

BACKGROUND OF THE INVENTION

1. Field of the invention

This invention relates to chemical compounds useful as chemicalintermediates in the preparation of valuable antibiotic substances.

2. Description of the prior art

There exists a need to provide alternate and more efficient methods ofproducing key intermediates necessary for the preparation of new andvaluable antibacterial agents. The new intermediate compounds andprocess for their preparation were heretofor unknown.

DETAILED EXPLANATION OF THE INVENTION

Compounds having the formula ##STR1## wherein -.sup.⊕ A represents##STR2## (wherein R² is a hydrogen atom or an amino group, and n is aninteger of 1 to 2); Y.sup.⊖ represents an anion; and R¹ represents alower alkyl group; are prepared by a process which comprises reacting7-amino-3-halogenomethyl-3-cephem-4-carboxylic acid of the formula##STR3## (wherein X is a halogen atom) with(tri-loweralkylsilyl)trifluoroacetamide of the formula ##STR4## (whereinR¹ is as defined above) and a pyridine compound of the formula (IV)##STR5## (wherein R² and n are as defined above).

If necessary, by releasing the protective groups [namely, (R¹)₃ Si-],7-amino-3-substituted-methyl-3-cephem-4-carboxylic acid (or carboxylate)of the formula ##STR6## are prepared.

Schematically, the reaction sequence may be illustrated as below.##STR7## (wherein X is a halogen atom) ##STR8## (wherein R² is ahydrogen atom or an amino group, and n is an integer of 1 to 2); Y.sup.⊖represents an anion; and R¹ represents a lower alkyl group; ##STR9##

This invention relates mostly to novel compounds and the processtherefor. More particularly, this invention relates to novel compoundswhich are useful as intermediates in the preparation of therapeuticallyactive cephalosporins, and to the processes for preparing suchcompounds.

It is an object of the present invention to provide chemicalintermediates which can easily converted to cephalosprins and othertherapeutically useful substances. It is another object of the presentinvention to provide a novel process for the preparation of thesecompounds.

The main objective of the present invention is the synthesis of valuablekey intermediates in the ultimate synthesis of particular finalcompounds, i.e. cephalosporins having a substituted pyridinio group atthe 3-position.

The primary objective of the present invention is to prepareintermediates that are readily converted into compounds disclosed in theinventors' co-pending patent applications such as U.S. patentapplication Ser. No. 656,162 and European Patent Application No. 84306967.5.

The present invention is explained in more detail below.

Examples of the pyridine compounds used for the reaction of the presentinvention are pyridine, 4-aminopyridine, 3-aminopyridine,2-aminopyridine, 2,3-cyclopentenopyridine, 5,6,7,8-tetrahydroquinoline,3,4-cyclopentenopyridine, 5,6,7,8-tetrayhydroisoquinoline, etc.

Examples of the group represented by -.sup.⊕ A are pyridinium,aminopyridinium ##STR10## 2,3-cyclopenteno-1-pyridinium ##STR11##5,6,7,8-tetrahydro-1-quinolinium ##STR12## 3,4-cyclopenteno-1-pyridinium##STR13## 5,6,7,8-tetrahydro-2-isoquinolinium ##STR14## etc.

Examples of the anion of the formula Y.sup.⊖ are inorganic anions suchas a halogen anion (Cl.sup.⊖, I.sup.⊖, etc.), and a sulfonate anion(HSO₄.sup.⊖, SO₄.sup.⊖⊖, etc.); and organic anions such as abenzenesulfonate anion (C₆ H₅ SO₃.sup.⊖), an acetate anion (CH₃COO.sup.⊖), a fumarate anion (HOOC--CH═CH--COO.sup.⊖), a citrate anion##STR15## etc.

Examples of "Halogen" in the foregoing definition are chlorine, bromine,iodine and fluorine.

Examples of "lower alkyl" are methyl, ethyl, propyl, butyl, iso-butyl,etc. Thus, typical lower alkyl is straight or branched carbon chainalkyl having 1 to 5 carbon atoms.

The compounds (prepared by the process of this invention) of the formula(I₁) are novel compounds. And, the compounds (prepared by the process ofthis invention) of the formula (I₂) except7-amino-3-pyridiniomethyl-3-cephem-4carboxylate (namely, ##STR16## arealso novel compounds.

A known process for producing the above known compound (namely,7-amino-3-pyridiniomethyl-3-cephem-4-carboxylate) are disclosed inunexamined Japanese patent application laid-open under the laying-openNo. Sho. 56-12397, and the known process comprises hydrolysingcefaloridin which is known as a valuable antibacterial compound.However, this known process is not economical, and is not suitable forthe practical production of the compound.

The process of the present invention is entirely different from theknown process, and has a characteristic in that 7-amino-3-halogenomethylcephalosporanic acid (II), which is easily available, is used asstarting material. Further, the loweralkylsilyl compounds of thisinvention are easily soluble in organic solvents, and side reactionssuch as rearrangement of double bond at the 2-position of thecephalorsporin nucleus (Δ³ →Δ² rearrangement) do not occur in theprocess of this invention even when reacting nucleophilic reagent suchas pyridine compounds. Thus, the process of this invention exhibits highyield and high purity.

So, the process of this invention is excellent in case of industrialmanufacturing of cephalosporin compounds.

In the process of this invention,7-amino-3-halogenomethyl-3-cephem-4-carboxylic acid (II) or a saltthereof is reacted with (tri-loweralkylsilyl)trifluoroacetamide (III₁ orIII₂) and pyridine compound (IV) in an organic solvent which is inertfor the reaction.

As (tri-loweralkylsilyl)trifluoroacetamide, is usedO,N-bis(tri-loweralkylsilyl)trifluoroacetamide (III₁) orN-methyl-N-tri-loweralkylsilyltrifluoroacetamide (III₂). Preferableexamples of the compounds (III₁) and (III₂) areO,N-bis(trimethylsilyl)trifluoroacetamide ##STR17##N-methyl-N-trimethylsilyltrifluoroacetamide ##STR18##

When reacting 7-amino-3-halogenomethyl-3-cephem-4-carboxyl acid with(tri-loweralkylsilyl)trifluroacetamide (III₁ or III₂) and pyridinecompound (IV), it is preferred that7-amino-3-halogenomethyl-3-cephem-4-carboxylic acid is, first, reactedwith (tri-loweralkylsilyl)trifluoroacetamide (III₁ or III₂), and thenwith pyridine compound (IV) (that is, 2 step reaction). However,(Tri-loweralkylsilyl)trifluoroacetamide (III₁ or III₂) and pyridinecompound (IV) can be reacted simultaneously with7-amino-3halogenomethyl-3-cephem-4-carboxylic acid.

The reaction proceeds easily at room temperature. When performing thereaction in 2 steps, the 1st step may be performed at room temperatureand the 2nd step may be performed under heating or cooling at atemperature from -20° C. to 40° C. Examples of the inert organic solventusually used are dichlromethane, acetone, acetonitrile, tetrahydrofuran,and chloroform.

In the process of invention, tri-loweralkylsilyl compounds (I₁) areproduced. The compounds (I₁) can be used, as it is, as startingmaterials for various cephalosporin compounds which may be valuableantibacterial agents. That is, the compounds (I₁) can be subjecteddirectly to the next reaction for producing the valuable cephalosporincompounds. However, the compounds (I₂) obtained after releasing thetri-loweralkylsilyl groups (protective groups) can be used as staringmaterials for producing the valuable cephalosporin compounds, ifnecessary.

The removal of the protective groups for the reaction product is easilyperformed, by treatment with water or alcohol-solvent. Examples ofalcohol are mono-OH alcohol (such as methanol, ethanol, propanol) anddi-OH alcohol (such as 1,2-ethanediol, 1,3-propanediol, 1,3-butanediol).It is preferred to use 1,3-butanediol, in view of the ease of separationand purification of the formed compounds.

The manufacturing process and the process of this invention will befurther explained by the following Reference-Examples and -Explanationand Examples. Reference explanation and Reference Examples show themanufacturing process for producing 7-substituted aminocephalosporincompounds by introducing a substituent at 7-amino position of thecephalosporin nucleus of the compounds of this invention.

Reference Explanation:

Cephalosporin derivatives claimed in the inventors' co-pendingapplications (U.S. patent application Ser. No. 656,162 and EuropeanPatent Application No. 84 306967.5) are prepared from the compounds ofthis invention by amidation (acylation) at the 7-amino group position inthe compounds of this invention by using suitable acylating agents. Thisamidation reaction is explained below. ##STR19## In the above formulae,○P is a hydrogen atom or a protective group for an amino group, ○P' is ahydrogen atom or a tri-loweralkylsilyl group; and ○Q is a hydrogen atomor a tri-loweralkylsilyl group; -A.sup.⊕ is as defined above.

Compounds I (valuable cephalosporin compounds) can thus be produced byreacting substituted oxyiminothiazolylacetic acid derivative or reactivederivative thereof with 7-amino-3-cephem derivative (I₁ and I₂) andthen, if necessary, releasing any protective group(s).

In this case the protective group for an amino group may be one usuallyused in the field of peptide chemistry and practical examples are acylgroups such as a formyl group, an acetyl group, a propionyl group, atert-butoxycarbonyl group, a methoxyacetyl group, a methoxypropionylgroup, a benzyloxycarbonyl group, a p-nitrobenzyloxycarbonyl group;tri-loweralkylsilyl groups such as a trimethylsilyl group; and aralkylgroups such as a benzyl group, a benzhydryl group (diphenylmethylgroup), a trityl group.

The reaction is usually performed in a solvent under cooling at roomtemperature or below. Any solvents which do not take part in thereaction can be used. Examples of the solvent usually used are organicsolvents such as dioxane, tetrahydrofuran, ether, acetone, ethyl methylketone, chloroform, dichloromethane, dichloroethane, methanol, ethanol,acetonitrile, ethyl acetate, ethyl formate, dimethylformamide dimethylsulfoxide; these solvents may be used alone or in appropriatecombination.

The acylating agent may be a free carboxylic acid or a reactivederivative thereof. Suitable examples of the compound are mixed acidanhydrides, acid anhydrides, acid halides, active esters, active amides,acid azides. When using the compound in the form of a free carboxylicacid, it is preferred to use a condensing agent such asN,N'-dicyclo-hexylcarbodiimide or N,N'-diethylcarbodiimide.

According to the kind of reactive derivative of carboxylic acid used, itmay be preferred for smooth reaction to operate in the presence of abase. Examples of such a base are inorganic bases such as sodiumhydrogencarbonate, potassium hydrogencarbonate, sodium carbonate,potassium carbonate; and organic bases such as trimethylamine,triethylamine, dimethylaniline, pyridine.

EXAMPLE 1 ##STR20##

In 10 ml of dichloromethane was suspended 680 mg of7-amino-3-iodomethyl-3-cephem-4-carboxylic acid and after adding thereto1.2 ml of O,N-bis(trimethylsilyl)trifluoroacetamide, the mixture wasstirred for 30 minutes at room temperature to form a clear solution. Thesolution was cooled to 5° to 6° C., and 316 mg of pyridine was addedthereto. After stirring the solution for 4 hours at the sametemperature, 1.6 ml of 1,3-butanediol was added thereto. Precipitatesthus formed were collected by filtration, washed with 30 ml ofdichloromethane, and dried to provide 730 mg of7-amino-3-(1-pyridiniomethyl)-3-cephem-4-carboxylic acid iodide.##STR21##

Using the compound of Example 1 as a starting material, the followingcompound was obtained.

Reference Example 1 ##STR22## (i) In 10 ml of dichloromethane wassuspended 419 mg of 7-amino-3-(1-pyridiniomethyl)-3-cephem-4-carboxylicacid iodide and after adding thereto 0.9 ml ofO,N-bis(trimethylsilyl)trifluoroacetamide, the mixture was stirred for30 minutes to form a clear solution. The solution was cooled to -40° C.,and 0.5 ml of pyridine was added thereto. (The solution thus formed ishereafter referred to as "Solution A".)

In 10 ml of dichloromethane was suspended 738 mg of(Z)-α-(2-tritylamino-4-thiazolyl)-α-[(2-tritylamino-4-thiazolyl)methoxyimino]aceticacid and after cooling the suspension to 3° to 4° C., 208 mg ofphosphorus pentachloride was added thereto, and the mixture was stirredfor 15 minutes at 3°-4° C. (The solution thus formed is hereafterreferred to as "Solution B".)

Solution B was added dropwise to solution A and the temperature of thereaction mixture was elevated to -10° C. over 15 minutes. After addingto the reaction mixture 1 ml of water, 1 ml of tetrahydrofuran and 3 mlof 1N-hydrochloric acid, the mixture was stirred for 10 minutes at-10°-0° C. The reaction mixture was distilled under reduced pressure toremove dichloromethane and tetrahydrofuran and after adding to theresidue obtained 50 ml of water, precipitates (powder) thus formed werecollected by filtration, washed with water, and dried to provide 0.91 gof a crude product (a compound having protective groups).

(ii) After adding to the crude product obtained as above 20 ml oftrifluoroacetic acid and 6 ml of water under ice-cooling, the mixturewas stirred for 1 hour at room temperature. Insoluble materials wereremoved by filtration, and the filtrate was concentrated under reducedpressure. To the residue was added 20 ml of ether, and the powder thusformed was collected by filtration to provide 0.45 g of a crude product.The crude product was suspended in 50 ml of water and after adding 2 mlof 1N-hydrochloric acid, the formed solution was subjected to columnchromatography on Diaioh HP-20 and the product was eluted first withwater and then with mixtures of water-methanol of successively changingmixing ratio. The fractions containing the desired product wereconcentrated, and lyophilized to provide 80 mg of(Z)-7-{α-(2-amino-4-thiazolyl)-α-[(2-amino-4-thiazolyl)methoxyimino]acetamido}-3-(1-pyridiniomethyl)-3-cephem-4-carboxylate.##STR23##

EXAMPLE 2 ##STR24##

In 50 ml of dichloromethane was suspended 1.7 g of7-amino-3-iodomethyl-3-cephem-4-carboxylic acid and after adding thereto2.8 ml of O,N-bis(trimethylsilyl)trifluoroacetamide, the mixture wasstirred for 30 minutes at room temperature to form a clear solution.After adding thereto 654 mg of 2,3-cyclopentenopyridine, the solutionwas stirred for 4 hours at room temperature to provide trimethylsilyl7-trimethylsilylamino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylateiodide. After adding thereto first 4 ml of 1,3-butanediol, and thenadding 150 ml of ether, precipitates thus formed were collected byfiltration, washed with 50 ml of ether, and dried to provide 1.8 g of7-amino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylicacid iodide. ##STR25##

Using, as a starting material, trimethylsilyl7-trimethylsilylamino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylateiodide obtained in the reaction course of Example 2, the followingcompound was obtained.

Reference Example 2 ##STR26##

In 25 ml of dichloromethane was suspended 3.92 g of(Z)-α-(2-tritylamino-4-thiazolyl)-α-[(2-tritylamino-4-thiazolyl)methoxyimino]aceticacid and after cooling the suspension to 3° to 4° C. and then addingthereto 1.04 g of phosphorus pentachloride, the mixture was stirred for15 minutes at 3°-4° C. (The solution thus formed is hereafter referredto as "Solution A".)

A solution containing trimethylsilyl7-trimethylsilylamino-3-(2,3-cyclopenteno-1-pyridiniomethyl)-3-cephem-4-carboxylateiodide obtained in the reaction course of Example 2 was cooled to -50°C., and 2.2 ml of pyridine was added thereto. (The solution thus formedis hereafter referred to as "Solution B".)

Solution A was added dropwise to solution B, and the temperature of thereaction mixture was increased to -15° C. over 15 minutes. After addingthereto 5 ml of water, 10 ml of tetrahydrofuran, and 10 ml of1N-hydrochloric acid, the resultant solution was stirred for 10 minutesunder ice-cooling. The reaction mixture was distilled under reducedpressure to remove dichloromethane and tetrahydrofuran and after addingto the residue obtained 200 ml of water, precipitates thus formed werecollected by filtration. The precipitates obtained was washed withwater, and dried to provide 5.5 g of a crude product (a compound havingprotective groups). After adding to the crude product 60 ml oftrifluoroacetic acid and 12 ml of water under ice-cooling, the mixturewas stirred for 1 hour at room temperature. Insoluble materials wereremoved by filtration, and the filtrate was concentrated under reducedpressure. To the residue was added 150 ml of ether to form a powder, andthe powder was collected by filtration to provide 2.7 g of a crudeproduct. The crude product was suspended in 200 ml of water and afteradding thereto 4 ml of 1N-hydrochloric acid, the formed solution wassubjected to column chromatography on Diaion HP-20 and the product waseluted first with water and then mixtures of water and methanol ofsuccessively changing mixing ratio (water:methanol from 10:1 to 10:6).The fractions containing the desired product were concentrated, andlyophilized to provide 275 mg of(Z)-7-{α-(2-amino-4-thiazolyl)-α-[(2-amino-4-thiazolyl)methoxyimino]acetamido}-3-(2,3-cyclopenteno-1-pyridinyl)-3-cephem-4-carboxylate.##STR27##

EXAMPLE 3 ##STR28##

In 50 ml of dichloromethane was suspended 1.7 g of7-amino-3-iodomethyl-3-cephem-4-carboxylic acid and after adding thereto2.8 ml of O,N-bis(trimethylsilyl)trifluoroacetamide, the mixture wasstirred for 30 minutes at room temperature to form a clear solution.After adding thereto 665 mg of 5,6,7,8-tetrahydroisoquinoline, thesolution was stirred for 4 hours at room temperature to providetrimethylsilyl7-trimethylsilylamino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylateiodide. After adding thereto first 4 ml of 1,3-butanediol, and thenadding 150 ml of ether, precipitates thus formed were collected byfiltration, washed with 50 ml of ether, and dried to provide 2 g of7-amino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylicacid iodide. ##STR29##

Using, as a starting material, trimethylsilyl7-trimethylsilylamino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylateiodide obtained in the course of the reaction of Example 3, thefollowing compound was produced.

Reference Example 3 ##STR30##

In 25 ml of dichloromethane was suspended 3.92 g of(Z)-α-(2-tritylamino-4-thiazolyl)-α-[(2-tritylamino-4-thiazolyl)methoxyimino]aceticacid and after cooling the suspension to 3° to 4° C. and then addingthereto 1.04 g of phosphorus pentachloride, the mixture was stirred for15 minutes at 3°-4° C. (The solution thus formed is hereafter referredto as "Solution A".)

A solution containing trimethylsilyl7-trimethylsilylamino-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylateiodide in the reaction course of Example 3 was cooled to -50° C., and2.2 ml of pyridine was added thereto. (The solution thus foremd ishereafter referred to as "Solution B".)

Solution A was added dropwise to solution B, and the temperature of thereaction mixture was increased to -15° C. over 15 minutes. After addingthereto 5 ml of water, 15 ml of 1N-hydrochloric acid, and 10 ml oftetrahydrofuran, the resultant solution was stirred for 10 minutes underice-cooling. The reaction mixture was distilled under reduced pressureto remove dichloromethane and tetrahydrofuran and after adding to theresidue obtained 200 ml of water, precipitates thus formed werecollected by filtration to provide 10 g of a crude product containingwater (a compound having protective groups). After adding to the crudeproduct 70 ml of trifluoroacetic acid and 14 ml of water underice-cooling, the mixture was stirred for 1 hour at room temperature.Insoluble materials were removed by filtration, and the filtrate wasconcentrated under reduced pressure. To the residue was added 200 ml ofether to form a powder, and the power was collected by filtration toprovide 4 g of a crude product. The crude product was suspended in 300ml of water and after adding 6 ml of 1N-hydrochloric acid, the formedsolution was subjected to column chromatography on Diaion HP-20 and theproduct was eluted first with water and then mixtures of water andmethanol of successively changing mixing ratio (water:methanol from 10:1to 10:7). The fractions containing the desried product wereconcentrated, and lyophilized to provide 393 mg of(Z)-7-{α-(2-amino-4-thiazolyl)-α-[(2-amino-4-thiazolyl)methoxyimino]acetamido}-3-(5,6,7,8-tetrahydro-2-isoquinoliniomethyl)-3-cephem-4-carboxylate.

We claim:
 1. A process for the preparation of7-amino-3-substituted-methyl-3-cephem-4-carboxylic acid or carboxylaterepresented by the general formula (I₂)wherein --.sup.⊕ A represents##STR32## wherein R² is a hydrogen atom or an amino group, and n is aninteger of 1 to 2; Y⁻ represents an anion selected from the groupconsisting of halogen, sulfonate, benzenesulfonate, acetate, fumarateand citrate anions, which comprises reacting, in an inert, organicsolvent and at a temperature of from about -20° to about 40° C.,7-amino-3-halogenomethyl-3-cephem-4-carboxylic acid of the formula (II)##STR33## wherein X is a halogen atom selected from the group consistingof chlorine, bromine, iodine and fluorine, with(tri-lower-alkylsilyl)trifluoroacetamide of the formula ##STR34##wherein R¹ is a lower alkyl group and a pyridine compound of the formula(IV) ##STR35## and then releasing the tri-loweralkylsilyl protectivegroups of the formed compound of the formula ##STR36##
 2. A process forthe preparation of tri-lower-alkylsilyl derivatives represented by thegeneral formula ##STR37## wherein --.sup.⊕ A represents ##STR38##wherein R² is a hydrogen atom or an amine group, and n is an integer of1 to 2; Y.sup.⊖ represents an anion selected from the group consistingof halogen, sulfonate, benzenesulfonate, and citrate anions; andR¹represents a lower alkyl group; which comprises reacting, in an inertorganic solvent and at a temperature of from about -20° to about 40° C.,7-amino-3-halogenomethyl-3-cephem-4-carboxylic acid of the formula##STR39## wherein X is a halogen atom selected from the group consistingof chlorine, bromine, iodine and fluorine, with a(tri-loweralkylsilyl)trifluoroacetamide of the formula ##STR40## and apyridine compound of the formula (IV) ##STR41##
 3. A process for thepreparation of 7-amino-3-substituted methyl-3-cephem-4-carboxylic acidof the formula (I₂) ##STR42## wherein --.sup.⊕ A represents ##STR43##wherein R² is a hydrogen atom or an amino group, and n is an integer of1 to 2; Y.sup.⊖ represents an anion selected from the group consistingof halogen, sulfonate, benzenesulfonate, acetate, fumarate and citrateanions, which comprises releasing the tri-loweralkylsily protectivegroups of the tri-loweralkylsilyl derivative represented by the formula##STR44## wherein --.sup.⊕ A represents ##STR45## wherein R² is ahydrogen atom or an amino group, and n is an integer of 1 to 2; Y.sup.⊖represents an anion as indicated above; and R¹ represents a lower alkylgroup.
 4. A process claimed in claim 1, 2 or 3 wherein R¹ is a methylgroup.
 5. A proces claimed in claim 1, 2 or 3 wherein X is a iodineatom, and Y is a iodine atom.
 6. A process claimed in claim 1, 2 or 3wherein Y is an inorganic anion.